Build Once, Deploy Everywhere

We were faced with an interesting problem. We want to build once and deploy the build to multiple environments for testing, staging and ultimately consumption in production. Well in addition to build once, we also want to allow remote debugging. We need to build in debug mode to get pdb generated and have other configurations that will allow debugging. Yet, we don’t want to deploy a debug build to staging or production. What do we do?

The thought right now is to do a debug build and create to packages, one for debug and one for release. To do this we would have to strip out the pdb and turn on debugging in the release package. So, we still have one build, but we have two flavors of packages.

I am not yet sure if this is viable, hence the reason I am blogging this out. First I need to fully understand the difference between a debug and release build in MSBuild. I have an idea, but I need to verify my assumptions.

Difference Between Debug and Release Build

What I have found is the main difference between debug and release building are:

Debug build generates pdb files.

Release build instructs the compiler to use JIT optimizations.

PDB files are symbol databases that allow a debugger to map machine code to source code (actually MSIL) so you can set break points in source code and the debugger can halt execution of the machine code. This is probably a terrible explanation, but you should get the gist.

JIT optimizations are things the compiler does to speed up the execution of your code. It may reorganize loops to make them run faster and other little magic tricks that happen under the cover that we usually never have to worry about.

Now What?

After doing this research I learned a lot about building .Net code, but I also realized that I am taking this a little to far. My primary goal is that we build our application once and use that build in multiple environments to get it tested and deployed to production. When we need to do a remote debug we are using researching an issue and there is no reason that we couldn’t flip a switch on one particular build so that it builds in debug mode, deploy it to a test environment, debug it, make some fixes after finding the cause of the issue we are debugging, then flip the switch back to release and build again, this time allowing the build to go all the way to production.

Issues

The problem here is that we need to make sure that we do not allow debug builds to make it into production. My initial thought is to mark debug builds with a version that is tagged with DEBUG. Then I can have logic in the production deploy that checks for the DEBUG tag and fail the deploy if it is present. We can do the same for pdb files and web.config. Specifically, check for inclusion of pdb (we shouldn’t have pdb file in production). We can also have logic that checks for debug=true and other configurations that we don’t want leaking into production.

We would have to alter our deployment pipeline to add a job that will do these checks based on the environment being deployed. We would have to also look at maybe putting debug builds in a different artifact repository to keep them segregated from release candidates. This would also cause another change to the deployment pipeline where we check the release candidate or debug repository based on some setting.

Conclusion

This would be a lot of changing to our pipeline, but I believe it is worth it in the long run. It also prevents us from leaking manual processes into how we build and deploy the app.